In conventional display devices, a color filter (CF) including filter elements corresponding to red, green, and blue (RGB) is used. In a display device with such a color filter, white light emitted from a backlight (backlight light) enters an RGB color filter arranged for each pixel and light of red, green, and blue is absorbed in each color filter to display a color image. In this display device, a color filter of each pixel absorbs light of wavelength different from red, green, and blue, and thus, the backlight light is not used sufficiently. Thus, conventionally, a color separation device including, for example, a prism (diffraction grating) and a lens is used to efficiently use the backlight light. With the color separation device, the backlight light is separated into wavelengths of red, green, and blue, and then, light of wavelength passes its corresponding color filter.
However, light separated by the color separation device has an angle dependency per color. Thus, light passing the color filter is diffused into different angle directions, and the color and the brightness tend to change depending on the viewing angle.
In order to solve such a problem of angle dependency with respect to color and brightness, conventionally, (1) disposing optical parts of lens (Fresnel lens) and a prism (diffraction grating) above and below each pixel in order to concentrate light biased to a specific direction to the front, and (2) disposing a diffusion plate of strong Haze are proposed. However, the method of (1) requires optical parts to concentrate the light biased in a specific direction to the front, and thus, costs increase. Furthermore, the method of (2) only eases a shift of exit angle, which does not give an effective solution, and may cause a significant decrease in the brightness of the front side.